Field of the Invention
This invention relates to an isolated Pediococcus acidilactici 05B0111 having high exopolysaccharide-producing ability. The Pediococcus acidilactici 05B0111 was deposited in Biosource Collection and Research Center (BCRC) of Food Industry Research and Development Institute (FIRDI) under accession number BCRC 910420 and deposited under the Budapest Treaty on the International Recognition of the Deposit of Microorganisms for the purpose of Patent Procedure on Mar. 5, 2009 with the International Patent Organism Depositary Deutsche Sammlung von Mikroorganismen and Zellkulturen GmbH (DSMZ), Inhoffenstr. 713, D-38124 Braunschweig, Germany under accession number DSM 22345. This invention also relates to a method of producing an exopolysaccharide, which comprises cultivating an isolated Pediococcus acidilactici in a suitable medium under condition such that the exopolysaccharide is formed. This invention also relates to a pharmaceutical composition containing the isolated Pediococcus acidilactici 05B0111 and to a food product containing the isolated Pediococcus acidilactici 05B0111.
Background Information
Exopolysaccharides (EPS) or extracellular polysaccharides (EPS) are macromolecules produced by microorganisms and secreted outside the cell wall of the microorganisms. EPS are generally classified into (1) capsular EPS that form a slime layer loosely attached to a cell surface and (2) unattached EPS that can be secreted to an environment.
Lactic acid bacteria (LAB) are generally recognized as safe (GRAS), and are widely used probiotics. A number of LAB are able to produce EPS. Most of EPS-producing LAB belong to the genus Streptococcus, the genus Lactobacillus, the genus Lactococcus, the genus Leuconostoc, or the genus Pediococcus (Petronella J. Looijesteijn et al. (1999), Applied and Environmental Microbiology, 65:5003-5008; T. Smitinont et al. (1999), International Journal of Food Microbiology, 51:105-111 Patricia Ruas-Madiedo et al. (2007), Applied and Environmental Microbiology, 73:4385-4388). In addition, some strains belonging to the genus Bifidobacterium are also shown to have the ability to produce EPS (P. Ruas-Madiedo and C. G. de los Reyes-Gavilan (2005), J. Dairy Sci., 88:843-856).
Generally speaking, EPS generated by LAB can be categorized as homopolysaccharides (Ho PS) and heteropolysaccharides (He PS). Ho PS are composed of a single type of monosaccharide. Examples of HoPS include α-glucans (e.g., dextran), β-glucans, and fructans (e.g., levan-type and inulin-type fructans). HePS are composed of repeating units that include different mono saccharides. The repeating units of HePS are normally composed of 3-8 monosaccharides, and mostly include D-glucose, D-galactose, and L-rhamnose. In a few cases, He PS include N-acetylglucosamine, N-acetylgalactosamine, fucose, glucuronic acid, and non-carbohydrate substituents (e.g., phosphate, acetyl group, and glycerol).
EPS produced by LAB are capable of enabling food to have special rheological properties and texture, thereby frequently serving as viscosifiers, stabilizer, emulsifiers, and gelling agents in the food industry. Additionally, many good effects of EPS produced by LAB on health of hosts have been discovered, for example, reduction in cholesterol, modulation of immune activity, antitumor, etc. Since EPS produced by LAB are beneficial to bioactivity, the same has been widely used.
However, EPS produced by bacteria are usually unstable, and yield of the same is normally very low. Since EPS is in great demand, various factors affecting productivity of EPS of LAB have been investigated so as to develop a new cultivation technology for increasing yield of EPS. Petronella J. Looijesteijn et al. mention that strains, culture conditions, and medium composition influence the amount of microbial EPS produced by a certain species, and that a type of a carbon source strongly affects productivity of EPS and may influence composition of EPS as well. Petronella J. Looijesteijn et al. further state that Lactobacillus delbrueckii subsp. bulgaricus NCFB 2772 generates three times more EPS using glucose than using fructose as a carbon source, and that yields of EPS produced by Lactobacillus casei CG11, Lactobacillus rhamnosus C83, and Streptococcus sali vari us subsp. Thermophilus are obviously affected by a carbon source (Petronella J. Looijesteijn et al. (1999), supra).
P. Ruas-Madiedo and C. G. de los Reyes-Gavilan mention that production of EPS by Lactobacillus casei CRL87 is 1.7-fold higher in galactose than in glucose, and that Lactococcus lactis subsp. Cremoris B40 produces larger amounts of EPS in glucose than in fructose (P. Ruas-Madiedo and C. G. de los Reyes-Gavilan (2005), supra). T. Smitinont et al. have reported that two Pediococcus pentosaceus strains (AP-1 and AP-3) isolated from traditional Thai food are capable of producing EPS in high yield, and that in liquid media containing 2% sucrose as a carbon source, AP-1 and AP-3 strains are able to respectively produce 6.0 g/L EPS and 2.5 g/L EPS (T. Smitinont et al. (1999), supra).
In addition, among known species belonging to the genus Pediococcus, Pediococcus damnosus, Pediococcusparvulus, and Pediococcus pentosaceus are able to produce EPS (Mai to Duenas et al. (2003), International Journal of Food Microbiology, 87:113-120; S. Velasco et al. (2006), International Journal of Food Microbiology, 111:252-258; T. Smi tinont et al. (1999), supra). However, the applicants indicate that none of literatures or prior art has disclosed the exopolysaccharide-producing ability of Pediococcus acidilactici and applications thereof.
During research, the applicants found that Pediococcus acidilactici has exopolysaccharide-producing ability. Particularly, the applicants have screened a Pediococcus acidilactici isolate, which is phylogenetically different from the published Pediococcus strains, from fermented food products. The Pediococcus acidilactici isolate has great exopolysaccharide-producing ability, thereby being expected to generate a large number of EPS.